Engine temperature and cowl flap control for aircraft ground trainers



Feb. 7, i956 F. M. BURELBACH ENGINE TEMPERATURE AND cowE FEAR CONTROLFiled Dec.

FOR AIRCRAFT GROUND TRAINERS /A/VEA/TOR BV F. M. BURELBACH Patented Feb.7, 1950 UNITED STATE ENGINE TEDIPERATURE AND COWL FLAP CONTROL FORAIRCRAFT TRAIN ERS GROUND Frederick M. Burelbach, Cranford, N. J.,assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of New York Application December 28, 1946, Serial No.719,091

8 Claims. (Cl. 35-13) This invention relates to ground trainers foraircraft and more particularly to circuits for simulating the automatictemperature control of the engine cowl flaps.

In certain types of airplanes, provision is made to automaticallycontrol the engine cowl aps of the engine so that such engine mayoperate at the temperature which will be conducive to its most efficientoperation. The engine cowl aps are arranged to be controlled manually bythe pilot but he may at any time enable them to be controlledautomatically in accordance with the rise or fall of the cylindertemperature of the engine. Should the cowl aps be open when the controlis switched to automatic operation, and the engine cylinder temperatureshould fall below a specied amount, for example 240 C., or a temperaturebelow the most efficient operating temperature, the cowl flaps willautomatically close and remain closed until the engine cylindertemperature rises to some value above 240 C. when the cowl flaps willautomatically open.

It is therefore the object of the present invention to provide in anairplane trainer, apparatus which simulates the automatic regulation ofthe engine cylinder temperature by controlling the amount of the openingof the engine cowl iiaps.

To attain this object in a trainer, the control of the engine cowl napsby the operation of the cowl naps control switch by the pilot, issimulated by a cowl flaps motor unit, the shaft of which is driven by` areversible motor to positions representative of the open and closedpositions of en-v gine cowl naps. The position to which the shaft isrotated is communicated telemetrically to an indicator at an instructorsdesk which indicates the position to which the pilot has operated theengine cowl aps.

Provision is also made for simulating the automatic control of theengine cowl flaps when the pilot operates his control switch to theautomatic position. A previously stated, in the airplane when the cowlflaps are placed by the pilot under automatic control, they are openedor closed in accordance with the rise or fall of the engine cylindertemperature. In the trainer a motor unit is provided which is controlledto rotate its shaft into a position representative of the assumed enginecylinder temperature. This shaft is provided with cams whic-h controlswitches, one of which causes the opening of a circuit of a rst relaywhen the shaft rotates to a position representative of a temperaturegreater than 244 C.

andthe other of which cams closes the circuit of` a second relay whenthe shaft rotates to a position representative of a temperature greaterthan 240 C. These relays cooperate, if the pilot has operated the cowlflaps control switch to its automatic position, to control the cowlflaps motor unit to operate to a position representativeof a closedcowlflaps condition if at the t1me itis in a position representative of anopen cowl flaps position and the relays are operated to positionsrepresentative 'of a decrease in engine cylinder temperature below 240C. or, to thereafter operate to a position representative of an opencowl flaps condition if the relays are op.

position of the slider of a potentiometer which isy driven to a positionrepresentative of the true air speed of the simulated flight. y l For aclearer understanding of the invention and the mode of its operation,reference may be had to the following detailed description thereof whening rheostats R2 and R3.

read in connection with the single sheet of drawing.

The cylinder temperature motor unit, disclosed in the upper portion ofthe drawing, is of the type fully disclosed-in Patent No. 2,428,767granted to.`

Albert, Davis, ,`Gumley, and Holden, October 14, 1947. The motor unitcomprises a first dualvacnum tube VTI which serves as a two-stage re--sistance coupled amplifier to amplifythe control signal applied to thecontrol grid of the first unit from the slider of the gain controlrheostat Rt which is connected to the input signal conductor |00, and toapply the amplified signal potential to the primary'winding of thestep-up transformer TI. The amplified signal is impressed from the lowersecondary winding of the transformer through the dual diode tube VTZ,serving as a full wave rectier, upon the control grid of the thyratrontube Ml. The signal is also impressed from the upper secondary windingof the trans-.

former upon'the control grid of the thyratron tube R. Grid biases areapplied to the control grids of the tubes MI and R from the source IDIof filament heating current IOI through the dual grid bias-- diode tubeVT3 and are adjusted by the of 115 volt alternating current. 'When theshaded pole winding |02 is short circuited and the main eld winding isenergized, the' motor 'JTMv rotates in one direction and when the shadedpole winding |03 is short circuited and the main iield winding isenergized, the motor .rotates in the oppof,

site direction.

Cathode heater current is supplied to the iilaw ments of all of thetubes fromL the source iii. Anode potential is supplied to vthe anoderof the left unit of tube VTi from the +130 volt source of directcurrent, through resistors |04 and |65, andto the anode of the rightunit of tube VTi through resistor Hit, the primary winding oftransformer TI and normal contacts ofthe test jack J. Anode potential issupplied to the anode of tube MI from the 115 volt source of potential|96, through ballast resistance lamp lill, the Winding of relay Minparallel with resistor |433 and through choke coil ||),3and to theanode tuoe R from the same source, through lamp resistance |01, throughthe winding oi relay RV in parallel f with resistor lle and through thechoke coil .i i l The motor TM, through the reduction gear box i l2,drives the .shaft ||3 in onefor` the other direction dependent upon theoperated or unoperated condition of the reversing relay RV, at a slowspeed and, through pairs of gears such as I-l, ||5 and H6, IVI, drivesthe sliders of po tentiometers CTI and CT2. Shaft ||3 also has securedthereto, Vcams H8 and |29 which oontrol the contacts of the L-`| and L2limit switches to cause the rotation of thefmotor TM to cease when thesliders of the potentiometers approach of an increase in venginecylinder temperature l above 244 C. and cam |2| being so shaped that thecontacts of switch A2 are not operated to their alternate position untilthe lshaft H3 hasl rotated to .a position representative of an increasein engine temperature above 240 C.

The true air speed motor unit disclosed schematically in the rightportionof the drawing is .of the same .general type as the cylindertemperature motor unit but to simplify the drawing `only that one of thepotentiometers driven thereby which `enters into the operation .oi thecircuits under consideration .has been disclosed.

The cowl flaps motor unitdisclosed in the lowler portion of the drawing,comprises a reversible shaped Apole motor CFM which, through the reduction gear box |22, vrotates the shaftv |23 in one direction or theother at `a slow speed den pendent Aupon which of the shaded pole windnings `|24 or |25 of the motor isshort circuited. The shaft V|23 throughthe gears |25, l2? and |28, |29, drive the sliders of potentiometers CFIand CF3 and lrotates cams Maand 4| 3| which control the limit switchesOpen vand Close, re-

spectively. g. H

" also be assumed that the pilot `has operated the shown) The right`units of the cylinder temperature indicators |32 and |33 at the pilotsstation in the trainer and at the instructors desk are controlled by thepotentiometer GT2 of the cylinder temperature motor unit for thesimulated right engine of the trainer. If the trainer, as assumed.y isarranged to simulate a two-engined airplane, a second cylindertemperature motor unit and a corresponding cowl iiaps motor unit wouldbe provided for the second simulated engine and the left units of thedual indicators |32 and |33 would be controlled by a potentiometer ofthe second cylinder temperature motor unit corresponding topotentiometer CTZ.

A cowl iiaps control switch is provided at the pilots station for eachof the assumed engines,

`the `switclfi for Controlling the cowl flaps of the right engine beingshown at |34. At the instructors desk a dual indicator |35 is provided,one unit of which is controlled by the potentiometer CFB -of the cowlflaps motor Iunit for the right .engine and the other unit vof which iscontrolled by a similar potentiometer driven by the cowl ilaps motorunit for the left engine (not The vinstructor is also provided with keys'by means of which he may at will disable the automatic operation of theengine cowl flaps motor units in simulation of the 4failure of theequivalent apparatus of an airplane.

of the right engine, potential of phase ol is applied to signal inputconductor |06 of the cylinder temperature motor unit for the rightengine representative of thev increase of cylinder temperature due tothe engine operation. It will cowl flaps switches to their Openpositions. With the control switch |34 in its Open position, an obviouscircuit is established 4for the OP relay |36 which operates and closes acircuit for lighting the Open ylarnp |31 at the instructors desk andcloses an obvious circuit for the 0 relay |38 of the cowl flaps motorunit for the right engine. With relay |38 operated, a short circuit isestablished for the right hand shaded pole winding |25 of the motor CFMextending from ground, over the contacts of relay E3B, over the contactsof limit switch Open and the winding |25 to ground. With the main statorwinding of the motor energized from a source of 115-volt alternatingcurrent, the motor CFM is operated in a direction to drive ythe slidersof potenticmeters CFI yand CFS toward the No. '3 termiH nals of theirwindings. When the sliders approach such terminals cam |3 operatesswitch Open to its alternate lposition thereby opening the vshortcircuit of the shaded lpole winding |25 to stop the motor. The movementof the slider of potentiometer CF3 controls the indicator |35 at theinstructors desi: to show that the cowl flaps for the right engine havebeen fully opened.

Similarly, the cowl naps motor unit for the left Key -|58V fior theengine cowl flaps motor unit for the potential, potential of phase p2 isapplied through resistor |40, through the winding of the true air speedpotentiometer TA and through resistor v|4| to ground, but with no airspeed assumed at the time, the slider of this potentiometer will beatthe No. 1 terminal of its winding and therefore the minimum value ofphase p2 potential will be derived at such slider and applied throughresistor |42, through the winding of cowl flaps potentiometer CFI andresistor I 43 to ground. Phase p2 potential will therefore be derived atthe slider of potentiometer CFI and applied as described throughresistor |39 to signal input conductor |00. It will be noted that withthe potentiometers TA and CFI connected as described, the Iphase p2potential, representative of the loweringof the cylinder temperature,will increase as the air speed increases and as the cowl flaps open.

` The summation of the potentials applied to conductor is amplied by thetwo units of ampliner tube VTI and is applied to the input transformerTI. Through the response of tubes VTI and VT2, VT3 and MI of thecylinder temperature motor control unit, the M relay is caused tooperate and with tube R not ring in response to the predominating phasep| signal, and consequently relay RV not operated, a short circuit isestablished from ground over the upper contacts of relay M, over theupper back contact of relay RV, over the normal contacts of the L2 limitswitch and through the left shaded pole winding |03 of motor TM toground. Motor 'I'M is thereby caused to rotate shaft |I3 at a slow speedin a direction representative of an increase in temperature. The slidersorf .potentiometers CTI and CTZ are now rotated towards the No. 3terminals of their windings. As the slider of balancing potentiometerCTI advances, potential of phase p2 in increasing value is appliedthrough resistor 44 to the signal input conductor |00 until, when suchpotential balances the signal potential of phase pI applied to suchconductor, no signal potential is applied to the control grid of theleft unit of amplifier tube VTI and relay M therefore releases and themotor TM comes to rest. For deriving the phase (p2 potential at theslider of potentiometer CTI, the potentiometer winding is energized overa circuit extending from the junction point between resistors |45 and|46 of the potential divider connected between the 402 bus bar andground. In response to the adjustment of the slider of potentiometerCT2, a circuit is established from the slider of suchv potentiometer,through the Calibrating rheostat CAL, through resistor |47 and thence inparallel through the right units of the cylinder temperature indicators|32 and |33 at the pilots station andat the instructors desk,respectively, and thence through resistor |48 to ground. The winding orfpotentiometer CTZ is energized by direct current from the +130 voltdirect current source through resistor |49 and thence through thepotentiometer winding to ground. 'I'he indicators will thus be set intopositions representative of the increase in cylinder temperature of theright engine. The indicators will show a gradual increase in readingfrom about 15 C. toabout 150 C. after an interval of about threeminutes.

The pilot may simulate the closing of the cowl flaps of the right engineby operating the control switch |34 to its Close position therebycausing the operation of the CL relay |50 which in turn establishes anobvious operating circuit for the C relay of the cowl flaps motor unitfor the right engine. The fact that the pilot has so operated the switch|34 is indicated to the instructor by the lighting of the Close lamp |52under the control of relay |50. With the C relay |5| operated a circuitis established from ground over its contacts, over the contacts of theClose limit switch and through the left shaded pole winding |24 of themotor CFM to ground thereby shortcircuiting such winding to cause themotor to turn in a direction representative of the closing of the cowliiaps. When the sliders of potentiometers CFI and CF2 approach the No. 1terminals of their windings, representative of the closed position ofthe cowl aps, the cam |3| will operate the limit switch Close to itsalternate position thereby opening the short circuit of winding |24 tocause the motor to come to rest.

The movement of the slider of potentiometer CF3 controls the right unitof the control flaps indicator 35 at the instructors desk to indicatethat the cowl flaps of the right engine are closed. The movement of theslider of the potentiometer CFI decreases the phase o2 potential appliedto signal input conductor |00 of the cylinder temperature motor unit dorthe right engine whereupon the motor TM of such unit rotates the shaft II3 in a direction representative of an increase in cylinder temperature.Through the movement of the slider of potentiometer CTI toward the No. 3terminal of its winding, the phase p2 balancing potential appliedtherefrom to signal input conductor |00 is increased until a potentialbalance on conductor |00 is again attained. Through the movement of theslider of potentiometer 0T2 the right units of the cylinder temperatureindicators |32 and |33 at the pilots station and instructors desk,respectively, are controlled to show an increase in their readings whichwill result from the closure of the engine cowl flaps for the rightengine.

It will now be assumed that lthe cowl flaps of both engines are open andthat a cruising condition of ight is being simulated. The increase inbrake horsepower output of the engine during take-off and climbing willcause an increase in the phase p| potential applied to the signal in putconductor |00 of the cylinder temperature motor unit for the rightengine and a consequent increase in the temperature indicated by theindicators |32 and I 33, for example, to a value over 240 C., but whenthe brake horsepower is reduced for cruising and the phase qiI potentialapplied to the signal input conductor is thereby reduced, the readingsof the indicators will decrease. Also due to the simulated movement ofthe trainer and the consequent cooling effect of the air current passingthrough the open cowl flaps, the temperature readings will furtherdecrease. This is simulated in the trainer by the increase in phase p2potential applied to the signal input conductor |00 by the movement ofthe slider of the true air speed potentiometer TA as theair speedincreases. f The increase in phase p2 potential applied to conductor |00causes the motor TM of the cylinder temperature motor unit for the rightengine to run in a direction representative of a decrease in temperatureand will be indicated by the right units of indicators |32 and |33.

It will now be assumed that the pilot operates the cowl aps controlswitches such as I 34 for both engines to their Auto positions. Themovement of switch |34 establishes an obvious circuit for the AUT relay|53 which in turn establishes the circuit of the A relay |54 of the cowlap mctor unit for the right engine and establishes the engager? c'ircult'for 'the-AUT V152i at the insti-notaris desk -to inform theii-'ls'tructor that the :control switch has `neenoperated to theposition Yfor automaticoperation ci the cowl iaps of the lightengi-ne.

It will now he assumed `that the cylinder temperature for ther-ightvengine'decreases toa value below 246 C. Under this conditiontheswitches A!! aand E32-will be operated by earns .|20 v.and |21 to'the positions indicated in which `the relayl'i will :be -niaintainedoperated Janfd the relay7 "|5'1 will loe released, a circuit will now he'esl-,alpiished `vfrom'ground over the inner upper contacts loi relay|56, over the loweriback lContact of relay l?, over-'the lowerconta-ot., of relay i515', lover fthe contacts'of the Close vlimitswitch .and through-thalet Shaded pole winding mi of theniotor CFM etoground. The motor CFM wiil thereupon operate in la Edirectionrepresen'tative'of 'the closing of the cowl flaps whereupon 'theindicator `|35 will show la With fthe A relay F54 operated,

closingmovement of the cowl flaps for the right engine and thepotentiometer 'CF1 ywill `decrease the `qiZpotmi'tial'applied from itssliderto signal input conductor iilil of the oylinder temperature motorunit for the right engine.

:As `ipa'eviciusly described the `reduction fof the n value of 'thephase .o2 potential will result'f-inthe operationof them-eter "TM of thecylinder temperature motor unit in-a ldirection representative of anincrease in cylinder temperature. If vthe temperature continues toincrease 'luntil'it .reaches 240 C., the earn 12| will operate the-switoh vA2 to its alternate position thereby closing an obvious circuitfor the relay i5?. Until the temperature rises above 244 C. the cam Y|2|3 will maintain the switch Al 'operated to its alternate :positionandrolay. i to will. se maintained operated. With the motor 'IM of thecylinder tempera'ture motor unit still operating under the control `ofrelay M, a circuit will now be effective `from ground over the uppercontacts of relay M, over the upper back contact of relay RV, over theupper contacts of relay |57, over the lower front contact of relay |58,over the upper contacts of relayY tiill, over the contacts of the limitswitch Open and through the right 'shaded Vpole Winding i25'iof motorCFM to ground. Motor CFM will thereupon `operate in a directionrepresentative of the opening of the cowl yflaps whereupon the indicator|35 will show an opening movement Yof the cowl flaps for the rightengine and the potentiometer CFI wilt iucrease'the phase :p2 potentialapplied from t1. .lider of such potentiometer to signal input conductorH of the cylinder temperature motor unit for the rightengine,"representative of the cooling effect `ortho opening ,of the cowlIlaps. When this effect is suicient to prevent any further increase intemperature, relay M of the temperature motor unit will release therebystopping the inotor TM of the temperature motor unit and the motor CFMof thecowl flaps motor unit.

If the engine temperature yshould startte increase again and the motorTM of the cylinder temperature .motor unit should he started againthrough the operation of relay M, the short-circuit of the left shadedpole Winding of the motor CFM of the cowl flaps motor unit Willbe againestablished as previously described whereupon the motor CFM will operatein a direction representative of a further opening of the cowl ilaps.Thereby an increased potential of phase p2 will be applied from theslider of potentiometer CFIv to the signal input conductor |00 with theresult that the motori-TM will be brought to irestarrd Ythe A motorCFMwill alsos'top.

erfective'irom .fgr'ound over the inner upper 'con-- tairitsof :relay151, :over the lower back contact of relay M56, over the 'upperAcontacts of relay |53, oyerthe contacts 'of the limit sWitchOpen, and-vt'lrrough the right shaded pole winding k|25 offthe Imotor fCFM'torground. Motor CFM will thereupon rotate Ashaft |23 in a directionrepresentative I'of thefiurther "opening 'of the cowl naps' until, whenaiposi'tion representative of the-,full open lfconolition 1of `the flapsis reached, limit switohpe'n'will 'be operated 'and the motor CFM willcome toirest.

the indicated temperature is -between240 an'd24=4f`C.and the cowl napsare fully opened as fdescr'ibe'd and the Vtemperature decreases fclue tothe-.application of increased phase a2 Ipotentialliromfthel-slider ofpotentiometer CFI to signaliinput conductor ifG10,'the motorTM willthen, through the-operation of rre-lays M and RV, be operated to drivethe `'shaft H3 in a direction representative 'of a 'decrease 'intemperature. Under-this condition a circuit 'is established 'from groundover Vthe upper-contacts of relay M, 'over the 'upper front icon-tact ofrelay RV, over 'the upper `contacts of relaylnow operated due to theclosure of 'the switch Al Iby cam |28, over the loweriront contact Yofrelay il 5? 'which is now operated 'due 'to'the closureof switch A2`by'cam |-2`|,-'over the lower A'cox-rtacts `o'f `relay 'over the contactsof limit :switch Close and theno'e through the le'ft shaded pole'winding '|25 of niotor CFM of the cowl -flaps motor unit to grou-ndwhereupon Esuchrrnotor will drive the shaft -123 in aelireotionrepresentative of :a closing of the cowl f'flaps. Sr-hi's vrech-icas thecooling eirect fas represented Iby a reduction voi the phase #i2potential supplied Yfrom the slider fof the potentiometer-CFI to "signalinput conductor :|90 and consequently, 'the motor TM is brought to astop through ftherelease ofr'el'ays M Aand `RV and the operationofmotorCFM is arrested. This may ooour`flofoi'e the fshat |'23 has beenrotated to aip'osition representative of `a lfully 'closed positionfofthe cowl "aps.

Should -thefoooling eieot cause the motor TM tozdriyethe -shfaft lf3 toa position representative offa temperature below '240 C., the cam 12|will release switch lA2 and thereby release relay |51, but relay F1515will loe vmaintained operated. A circuit will the-n lbe Closed fromground `over the inner Supper v`eontac-ts'of relay 15S, over the lowerback 'contact-of relay |51, over thelower contaictsfof rel-ay |54, overthe `contacts of the limit tmeoifsfabove v24'4" the cowl fla-ps will befully opened. In the'- temperature range between 240 and 244 the cowlflaps opening will be suicient to prevent any change in temperature. TheValues of 240 and 244 have been arbitrarily selected and may be changedby the cuttings of the cams |20 and I2I.

In the foregoing description, only the automatic and manual control ofthe cowl flaps for the right engine have been described, but it is to beunderstood that in a trainer designed to simulate the operation of aplurality of engines, apparatus similar to that disclosed would beoperated in a similar manner for each of the other simulated engines.

What is claimed is:

1. In an aircraft trainer wherein the operation of an airplane engine issimulated, a motor, means operable by said motor to positionsrepresentative of the positions of engine cowl flaps, means forsimulating the change in engine cylinder temperature incident to theengine operation, means operated when the simulated temperature fallsbelow a predetermined value to cause said motor to operate said firstmeans to a position representative of a fully closed position of thecowl flaps and means operated by said first means to control said enginecylinder temperature simulating means in a manner representative of anincrease in temperature incident to the closing of the engine cowl naps.

2. In an aircraft trainer wherein the operation of an airplane engine issimulated, a motor, means operable by said motor to positionsrepresentative of the positions of engine cowl flaps, means forsimulating the change in engine cylinder temperature incident to theengine operation, means operated when the simulated temperature fallsbelow a predetermined value to cause said motor to operate said firstmeans to a position representative of the fully closed position of thecowl flaps, means operated by said rst means to control said enginecylinder temperature simulating means in a manner representative of anincrease in temperature incident to the closing of the engine cowl aps,and means operative when the simulated temperature rises above apredetermined value to cause said motor to operate said rst means to aposition representative of the opening of the engine cowl flaps.

3. In an aircraft trainer wherein the operation of an airplane engine issimulated, a motor, means operable by said motor to positionsrepresentative of the positions of engine cowl flaps, means forsimulating the change in engine cylinder temperature incident to theengine operation, means operated when the simulated temperature fallsbelow a predetermined value to cause said motor to operate said firstmeans to a position representative of a fully closed position of thecowl flaps, means operative when the simulated temperature rises above apredetermined value to cause said motor to operate said first means to aposition representative of the opening of the engine cowl flaps, andmeans controlled by said first means to control said temperaturesimulating means to maintain the simulated temperature between saidpredetermined low and high values.

4. In an aircraft trainer wherein the operation of an airplane engine issimulated, a first motor, means operable by said motor to positionsrepresentative of the positions of engine cowl flaps, a second motor,means operable by said second motor to positions representative of theassumed the engine operation, means operable in response totheoperationof said second motor when the simulated temperature rises abovea predeterminedvalue to causesaid rst motor to operate said vfirst meansin av manner representative of the opening ofthe lcowl aps, meanscontrolled by said first means to cause said second motor to graduallyIcome to rest when said firsty means has operated to aposition'reprentative of an opening-of the engine cowl flaps to a degreesuflicient to arrest the rise in cylinder temperature, and meanseffective upon theY arresting of the operation of said second motor toarrest the operation of said first motor. 1

5. In an aircraft trainer wherein the operation' of an airplane engineis simulated, a first motor, means operable by said motor to positionsrepresentative ofthe positions of engine cowl naps, a secondmotor, ashaft rotatable by said second motor to positions representative of theassumed cylinder temperature of an engine incident to the engineoperation, a cam operated switch operable byvsaid shaft when said shaftis rotated to a position representative of a cylinder temperature abovea predetermined value, a relay operable upon the closure of said switchfor causing said rst motor to operate said first means in a mannerrepresentative of the opening of the engine cowl naps, means controlledby said rst means to cause said second motor to gradually bring saidshaft to rest when said first means has operated to a positionrepresentative of an opening of the engine cowl flaps to a degreesufcient to arrest the rise in temperature, and means effective upon thearresting of the operation of said second motor to arrest the operationof said first motor.

6. In an aircraft trainer wherein the operation of an airplane engine issimulated, a rst motor, means operable by said motor to positionsrepresentative of the positions of engine cowl naps, a second motor, ashaft rotatable by said second motor to positions representative of theassumed cylinder temperature of an engine incident to the engineoperation, a iirst cam operated switch operable by said shaft when saidshaft is rotated to a position representative of a cylinder temperatureabove a predetermined value, a relay operable upon the closure of saidswitch for controlling said first motor to operate said rst means in amanner representative of the opening of the engine cowl flaps, meanscontrolled by said first means to cause said second motor to slow downthe rotation of said shaft representative of the cooling effect due tothe opening of the engine cowl flaps, a second cam operated switchopened by said shaft when said shaft rotates to a positionrepresentative of a rise in cylinder temperature above a predeterminedvalue, and a normally operated relay releasable upon the opening of saidlatter switch for causing said first motor to operate said rst means toa position representative of a fully opened condition of said enginecowl flaps.

7. In an aircraft trainer wherein the operation of an airplane engine issimulated, a first motor, means operable by said motor to positionsrepresentative of the positions of engine cowlflaps, a second motor, ashaft rotatable by said second motor to positions representative of theassumed cylinder temperature of an engine incident to the engineoperation, a ca-m operated switch operable by said shaft when said shaftis rotated to a position representative of a cylinder temperaasseoirture above a predetermined ValueI` a normally operated relay reloasablouponthe oaerationv of said switch. for eonirolling-` said rstmotl; tooperateA said rst means in amannervrepresentative ofthe closing of theengine cowl flaps, means controlled by said first-means to, cause saidsecond motor to gradually bring S,aid shaft to rest when said rstmeanshas operatedtdalposition representative of a closing of the engine cowlflaps to a degree. suleent to arrest the drop. in cylinder temperature,and means y eiectiveupon the arresting of the operation of said secondmotor to arrest thev operation olf-said rst motor.

8. In an, aircraft trainer wherein theoperation of an airplane engine issimulatedLa rirst motor., means operated by said `motor to positionslrepresentarme of the 1;:ositionsy of engine cowl-11ans, a second motoraY shaitrotatable by said second motor to. positions representativo`of;I the assumed cylinder temperature of an engine. ineidexiti to theengine operation al rst cam operated switch operable by said shaft-whensuchshaft is rotated to av position representative of ay cylinder tem--`peraturebolo-W a predetermined vaiolo,r a relay operable upon theopening ofvsaid switch for g5 12 controlling said frstniotor to operatesaid first means in a manner'representative of the closing ofthe enginecowl naps, means controlled by said first means to cause said secondmotor to slow down the rotation of said shaft representae tive of theheating effect due to the. closing of the engine cowl flaps, a secondcam operated switch opened by said shaft when saidv shaft rotates to aposition representative of a decrease in cylinder temperature below apredetermined value, and a relay releasable upon the opening of saidlatter switch for causing said rst motor to operate said rst means toaposition representative of a fully closed condition of said engine cowlflaps.

FREDERICK M. BURELBACH.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,372,741 Horsfeld Apr. 3, 19452,428,67 Albert Oct. 14, 1947;

